The present invention relates to a display device, in particular a display device for a combination instrument of a motor vehicle.
The present invention and its background information are explained here with respect to a display device for a combination instrument in a motor vehicle, although it can be used with any display devices, such as display devices for ships, aircraft, etc.
Electronic combination instruments for motor vehicles usually have a plurality of display devices which are accommodated in a common housing and can be read by the driver from the front side through a transparent cover panel. Both analog pointer-type display devices and digital display devices are generally used with such combination electronic instruments.
With analog pointer-type display devices, a pointer mounted on a shaft is driven by a controlled pointer drive to provide an analog display of information such as speed, rpm, coolant temperature, oil temperature, fuel tank level and the like on a corresponding dial or a scale device.
For some time, electro-optic display devices (also known as displays) have been used as digital display devices in such combination instruments in motor vehicles to display any desired information such as warning functions, radio displays, telephone displays, traffic control information, etc.
In the past mainly LED (LED=light emitting diode) displays have been used for this purpose. In addition, LCDs (LCD=liquid crystal display) have also been used, and in individual cases VFDs or vacuum fluorescent displays and even other exotic known technologies have been used for display devices, such as plasma displays.
Because of their mechanical design, in particular the electric contacting, these displays usually have an edge which projects at the side beyond the usable display surface. This edge area is typically 5 to 15 mm in size.
With the combination instruments in question, such displays are directly adjacent to pointer-type displays with dials or scales which must be lighted from the rear at night to permit good visibility and an attractive design. At the same time, the dials or scales should be arranged approximately in the same plane as the displays for design reasons.
However, the above-mentioned edge of the displays does not allow uniform lighting of the immediately adjacent areas from the rear using conventional methods such as fiber optics (German Patent No. 42 42 913 from MOTOMETER) or lighting wells (German Patent No. 44 22 828 from SAGEM).
Thus, the fact that lighting from the rear cannot be designed to be uniform and is thus not esthetic has proven to be a disadvantage with such combination instruments.
Furthermore, the edge of the displays is a previously unused area in the restricted space available on a combination instrument.
The display device according to the present invention has the advantage that overlapping of the scale device and the electro-optic display device is possible while at the same time guaranteeing uniform lighting.
This yields a more compact design for the mechanical construction and furthermore makes the display device according to the present invention more esthetically appealing. The display device according to the present invention is especially advantageous when larger displays claiming a large portion of the area of the combination instrument are used. The resulting small remaining area for dials can then be used more efficiently. In addition, it is possible to mask areas of any shape in the display area using dials and to light them uniformly with the rest of the dial.
The idea on which the present invention is based is to apply a thin luminous layer to the scale device by which the section of the scale device covering the electro-optic display device as well as the remainder of the scale device can each be lighted at least in part.
According to a preferred refinement, the electro-optic display device has a display area in its section covered by the scale device.
According to another preferred embodiment, the section of the scale device covering the electro-optic display device is transparent, translucent or recessed in some areas, so that the appearance of the scale device through the display area of the electro-optic display device can be influenced. This offers the particular advantage that the scales can be varied according to the operating conditions of the vehicle or according to the driver""s wishes through appropriate control of the electro-optic display device.
According to another preferred refinement, the scale device has a transparent plastic panel and a scale layer printed on one side.
According to another preferred refinement, the scale layer is printed on the side facing away from the observer. This design ensures a uniform depth impression with regard to the scale device and the electro-optic display device for the observer.
According to another preferred refinement, the luminous layer is applied to the scale layer.
According to another preferred refinement, the luminous layer is an electroluminescent layer.
According to another preferred refinement, the electroluminescent layer is integrated into an electroluminescent film which preferably has a thickness in the range of 0.3 to 0.6 mm. This results in only minimal unevenness between the scale device and the electro-optic display device.
According to another preferred refinement, the analog display device has a mechanical pointer which travels over a plane facing the observer above the scale device.
According to another preferred refinement, the electro-optic display device has an LED display and/or a vacuum fluorescence display.
According to another preferred refinement, the electro-optic display device has a liquid crystal display.
According to another preferred refinement, the polarization filter layer of the liquid crystal display and the carrier of the luminous layer together form one unit. This simplifies the mechanical design of the display device.